Television apparatus having large viewing screens have to include a housings of substantial depth, which is particularly annoying if the television tubes are large. Additionally, the weight of such apparatus with large tubes becomes substantial, since the weight of the tube increases rapidly with its size.
It has been proposed to reduce the depth of television apparatus by use of cathode ray tubes in which the beams providing the television (TV) display are deflected. The TV tubes are located laterally with respect to the imaging screen of the tube. The electron beam within the tube is accelerated and suitably controlled within the neck of the tube. The beam is then deflected by a suitably provided and negatively charged electrode, for deflection on the phosphorescent layer of the TV imaging screen. This solution does not substantially decrease the size of the apparatus, since the system to generate the beam still requires substantial space. The brightness of such arrangement is unsatisfactory. This system can be used only with relatively small screens since, if the size of the screen is increased, deflection cannot be obtained without distortion; the costs of such systems also escalate rapidly as the screen size increases.
It has also been proposed to place three cathode ray beam tubes next to each other which, in accordance with the base colors thereof, project separate part images over a tiltable deflection mirror to a projection screen located on the housing, the respective primary color images then being super-imposed on the screen (see U.S. Pat. No. 4,209,807, ARITA, and corresponding German Patent Disclosure Document DE-OS 28 53 831). This arrangement has not been found to be commercially suitable since, to provide the viewing image, the mirror and the viewing screen must be flipped into a viewing position and then the relative position of the mirror, viewing screen and TV tubes carefully adjusted. The apparatus, when open, is subject to dust and contamination, so that eventually disturbance spots and the like will occur on the viewing screen. The arrangement is large and, since it requires three TV tubes, expensive. For large-area projection, distortions and unsharp regions, similar to out-of-focus portions of the image, are practically unavoidable and arise particularly towards the edge of the screen. It is practically impossible to project the primary images from the three TV tubes in precise register over the entire projection surface.
The mirror system is open and exposed and, thus, light reflection on the mirror due to extraneous light and other light reflections result in decreased contrasts and annoying ghosts, which interfere with viewing of the TV display.